1. Field of the Invention
The present invention relates to an intramedullary fracture fixation device. More specifically, the present invention relates to such a device for fixation of fractures of the proximal femur, including intertrochanteric and subtrochanteric fractures.
2. Description of the Related Art
A variety of fracture fixation devices are known for treatment of femoral fractures. In particular, intramedullary devices are known which provide distinct advantages over known nail-plate combination devices, especially for subtrochanteric and femoral shaft fractures. A good background discussion of such an intramedullary (IM) rod and cross-nail (lag screw) assembly is provided by U.S. Pat. No. 3,433,220 issued to Zickel, which is herein incorporated by reference in its entirety.
Known intramedullary devices have also been designed for treatment of intertrochanteric and femoral neck fractures. For example, U.S. Pat. No. 4,827,917 issued to Brumfield and U.S. Pat. No. 5,032,125 issued to Durham et al., which are herein incorporated by reference in their entirety, each disclose an intramedullary device having an IM rod, a lag screw, a set screw. Additionally, the device of Durham et al. includes a sleeve and a compression screw.
A further excellent description of an intramedullary device similar to that of the present application is set forth in the published United Kingdom Patent Application 2 209 947 A, which again is herein incorporated by reference in its entirety. This reference discloses a basic assembly of an IM rod, a lag screw and a set screw.
The disclosures of all three of the above references are considered to establish the state of the art. Each of the devices disclosed thereby address the desirability of compression in the treatment of femoral fractures and particularly emphasize sliding compression.
Brumfield teaches a lag screw which has a threaded portion and a smooth portion. The threaded portion is at a distal end to be screwed into the femoral head. The smooth portion is provided intermediate the threaded distal end and a head portion. The lag screw is installed into an angled/inclined bore in the IM rod and screwed into the femoral head. The smooth portion of the screw slides within the bore such that the head portion abuts an outer cortex of the bone to provide the desired sliding compression.
Durham et al. teaches a lag screw, sleeve and compression screw combination for achieving sliding compression. The sleeve is designed to fit within the angled bore of the IM rod with a proximal end of the lag screw extending into the sleeve. Both the sleeve and the lag screw are "keyed" to prevent the lag screw from rotating within the sleeve while permitting the lag screw to slide within the sleeve. The proximal end of the lag screw has an internally threaded bore for receiving the compression screw, which is correspondingly threaded. The compression screw is screwed into the proximal end of the lag screw so as to slide the lag screw relative to the sleeve to provide the desired sliding compression.
UK 2 209 947 A teaches the use of a tool which puts a traction force on the lag screw in a direction away from the femoral head. Although not explained in detail, the tool abuts a sleeve which is placed temporarily on the outer cortex of the femoral shaft.